1. Field of the Invention
The present invention relates to a thin film magnetic head in general employed in a magnetic recording medium drive such as a magnetic disk drive, a magnetic tape drive, and the like. In particular, the invention relates to a thin film magnetic head comprising an upper auxiliary magnetic pole raised from the lower surface of an upper magnetic pole layer toward a lower magnetic pole layer, and to a method of making such a magnetic thin film head.
The thin film magnetic head of this type may be utilized in combination with a read head such as a giant magnetoresistive (GMR) element or the like, or may be utilized to read magnetic information data by itself.
2. Description of the Prior Art
The front ends of an upper and a lower magnetic pole layer cooperate with each other so as to define a write gap therebetween. The write gap serves to cause a magnetic field for recordation leaking out of a medium-opposed surface or bottom surface of a head slider. The width of the write gap determines the width of a recording track established on a magnetic recording medium. If the width of the front ends of the upper and lower magnetic pole layers can be reduced, the width of a recording track can be reduced. Accordingly, the density of recordation can be improved in the magnetic recording medium. Employment of a smaller upper auxiliary magnetic pole raised from the upper magnetic pole layer toward the lower magnetic pole layer is believed to reduce the substantial width of the write gap. Employment of a smaller lower auxiliary magnetic pole raised from the lower magnetic pole layer toward the upper magnetic pole layer is also believed to reduce the substantial width of the write gap. The upper and lower auxiliary magnetic poles are believed to greatly contribute to reduction in the width of a recording track over a magnetic recording medium. The density of recordation is thus supposed to get improved.
In general, a peak of the intensity can be observed in the magnetic field for recordation at the write gap in a thin film magnetic head. The aforementioned upper auxiliary magnetic pole induces sub-peaks of the intensity in the magnetic field at the edges of the upper magnetic pole layer laterally projecting from the upper auxiliary magnetic pole in the lateral direction of a recording track. The sub-peaks of the intensity at the edges of the upper magnetic pole layer leads to increase in the width of a recording track, reverse of the magnetization in the adjacent recording tracks, or the like. Unless the sub-peaks at the edges are reduced enough, it is impossible to realize an improved density of recordation over a magnetic recording medium.
In order to minimize the aforementioned drawback, the upper auxiliary magnetic pole should be shortened in the longitudinal direction of a recording track. In other words, the thickness of the upper auxiliary magnetic pole extending between the upper and lower magnetic pole layers has to be set at a predetermined value, possibly without an error. Heretofore, a method of making a thin film magnetic head has not been established to reliably controlling the thickness of the upper auxiliary magnetic pole. In particular, when a plurality of thin film magnetic heads are to be formed on a single wafer, a flattening treatment by a simultaneous grinding cannot establish a predetermined thickness in the upper auxiliary magnetic pole of every thin film magnetic head on the wafer.
It is accordingly an object of the present invention to provide a method of making a thin film magnetic head reliably establishing a predetermined thickness or height of a component without an error in the thin film magnetic head through a flattening treatment. In particular, it is an object of the present invention to provide a thin film magnetic head contributing to establishment of a predetermined thickness or height of a component without an error in the group of the thin film magnetic heads subjected to a simultaneous flattening treatment, as well as a method of making the same.
According to the present invention, there is provided a method of making a thin film magnetic head, comprising: forming a material piece standing in a space on the surface of a first material layer; forming a second material layer over the surface of the first material layer; forming a third material layer over the surface of the second material layer, said third material layer being less abrasive than the second material layer; and subjecting the third material layer to a flattening treatment until the material piece, embedded in the second material layer, gets exposed.
When the surface of the first material layer is covered with the second material layer, the material piece standing in a space on the first material layer is embedded within a swell formed on the surface of the second material layer. When the second material layer is thereafter subjected to the flattening treatment, such as grinding, the material piece gets worn off from the top along with the swell. The material piece is allowed to finally get exposed out of the surface of the second material layer. An accurate adjustment of the thickness of the second material layer leads to a reliable establishment of a predetermined thickness or height in the material piece with less error.
In general, a plurality of thin film magnetic heads are formed on a single wafer. It is difficult to establish a constant rate of abrasion for every thin film magnetic head on the wafer in the grinding. In this invention, the third material layer less abrasive than the second material layer is subjected to the grinding over a wider area just when the swell has completely been removed. Accordingly, the abrasion can be suppressed at the thin film magnetic head in which the swell has been removed, even when the other swells still exist on the wafer. In this manner, the third material layer can be utilized to hinder the abrasion in each of the thin film magnetic heads. The second material layer of a predetermined thickness reliably remains in each of the thin film magnetic heads on the wafer.
The method of making may be employed to form a thin film magnetic head comprising an upper auxiliary magnetic pole swelling from the lower surface of an upper magnetic pole layer, for example. In this case, the method may comprise: forming an upper auxiliary magnetic pole standing in a space on the surface of a lower magnetic pole layer; forming a first insulating layer over the surface of the lower magnetic pole layer; forming a second insulating layer over the surface of the first insulating layer, said second insulating layer being less abrasive than the first insulating layer; and subjecting the second insulating layer to a flattening treatment until the upper auxiliary magnetic pole, embedded in the first insulating layer, gets exposed.
When the surface of the lower magnetic pole layer is covered with the first insulating layer, the upper auxiliary magnetic pole standing in a space on the lower magnetic pole layer is embedded within a swell formed on the surface of the first insulating layer. When the first insulating layer is thereafter subjected to the flattening treatment, such as grinding, the upper auxiliary magnetic pole gets worn off from the top along with the swell. The upper auxiliary magnetic pole is allowed to finally get exposed out of the surface of the first insulating layer. An accurate adjustment of the thickness of the first insulating layer leads to a reliable establishment of a predetermined thickness in the upper auxiliary magnetic pole with less error. In addition, the second insulating layer less abrasive than the first insulating layer is subjected to the grinding over a wider area just when the swell has completely been removed in the same manner as described above. Accordingly, the abrasion can be suppressed at the thin film magnetic head in which the swell has been removed, even when the other swells still exist. In this manner, the first insulating layer of a predetermined thickness reliably remains in each of the thin film magnetic heads on the wafer.
The method of making may provide a thin film magnetic head comprising: an upper magnetic pole layer; a lower magnetic pole layer; a first insulating layer superposed over the surface of the lower magnetic pole layer between the upper and lower magnetic pole layers; and a second insulating layer disposed between the first insulating layer and the upper magnetic pole layer. The second insulating layer may have a property less abrasive than the first insulating layer. Since the aforementioned grinding is effected on the second insulating layer, a flattened surface can be defined between the second insulating layer and the upper magnetic pole layer.
Likewise, the method of making may provide a thin film magnetic head comprising: an upper magnetic pole layer extending rearward from its front end over a flattened surface; a lower magnetic pole layer extending rearward from its front end below the flattened surface; a non-magnetic gap layer interposed between the front ends of the upper and lower magnetic pole layers; a first insulating layer superposed over the surface of the lower magnetic pole layer between the upper and lower magnetic pole layers; and a second insulating layer superposed over the surface of the first insulating layer and defining the flattened surface. The second insulating layer may have a property less abrasive than the first insulating layer.
The thin film magnetic head may be employed tin a magnetic disk drive such as a hard disk drive (HDD), a magnetic tape drive comprising a magnetic recording tape as a magnetic recording medium, and the other types of a magnetic recording medium drive.